Documentation why to use/reuse existing classes

[jorainer]

Add description/details on benefits of re-using existing Bioconductor classes including concrete examples. Add that to the BioC contribution guide.

[jorainer]

@LiNk-NY @lshep can you maybe add the link to the github repo here and maybe point to the section where it would best fit.

[jorainer]

https://github.com/Bioconductor/pkgrevdocs

[jorainer]

See also issue #5 and #6

[LiNk-NY]

There are several places and they're a bit hidden in the docs. These sections should be more prominent. Perhaps we can create a proper classes "chapter" that encompasses #4, #5, and #6.

http://contributions.bioconductor.org/r-code.html#class-development

Mention (the new) classes chapter in

• http://contributions.bioconductor.org/general.html
• http://contributions.bioconductor.org/important-bioconductor-package-development-features.html